Magnesium base alloy



Patented Jan. 13, 1942 MAGhTESlIUM BASE ALLOY John C. McDonald, Midland, Mich, assignor to The Dow Chemical Company, Midland, Mich, acorporation of Michigan No Drawing. Application June 15, 1940,

Serial No. 340,784

4 Claims. (01. 75- 108) The invention relates to magnesium, base alloys and more particularly concerns an alloy of this nature having a high degree of formability associated with other desirable physical properties, such as high tensile and yield strengths.

Magnesium base alloys are being widely used in various structural and mechanical arts where a light weight metal is highly desirable, such as for use in making castings, forgings, and the like. However, the use of these alloys in the rolled form to make sheet metal articles requiring forming operations, such as bending, drawing,

and the like, has not progressed as rapidly due to the fact that in general alloys having good formability, permitting relatively sharp bends to be made without the article developing. external cracks, usually have inferior strength characteristics.

It is, accordingly, the principal object of the -invention to provide a magnesium base alloy which can be made into a rolled sheet or the like possessing a suflicient degree of ductility or formability to be sharply bent, drawn, or otherwise shaped, while having excellent tensile and yield strengths.

Other objects and advantages will be apparent as the description of the invention'proceeds.

My invention resides in the discovery that a magnesium base alloy composed of from about 0.01 to 6 per cent of lanthanum and from about 0.01 to 3 per cent of manganese, the balance being magnesium, possesses the aforementioned properties. The term magnesium used herein and in the appended claims is intended to in- 5 per cent elongation is to be regarded as a measclude magnesium containing the ordinary impurities that are found in the commercially pure metal, such as traces'of iron, copper, nickel, and

silicon. While the properties of good formability or ductility associated with high tensile and yield strengths are manifest over the entire range of composition indicated, I have found that in general the preferred combination of properties, such as the most desirable ductility for forming operations, as well as exceptionally high tensile and yield strengths, is obtained when the alloy contains from about 0.1 to 2 per cent of lan- 10 thanum and-from about 1 to 3 per cent of manganese.

The specific proportion of each alloying metal and the total amount of the alloying metals to be employed in the new alloy depends upon the 15 use for which the alloy is intended. For exam-v ple, in alloys where exceptionally high ductility or formability associated with good tensile and yield strengths is of principal importance, the alloy should contain from between about 0.1

20 to 1 per cent of lanthanum and from about 1 to 2 per cent of manganese. While in those instances where high yield and tensile strengths,

are of more importance, the lanthanum content of the alloy should be raised to from 2 to 6 per 2 cent.

The following table lists some of the properties of rolled sheet metal made from my new ternary alloy. and compares these properties with those of rolled sheet made from related binary alloys. A comparison of the properties illustrates the improvement in ductility and strength characteristics of the new alloy over that of the closely related binary alloys. In the table, the

ure of the ductility or formability of the specimen.

Table Noininal compos ion in per cent (maple. Annealed Cold rolled Slum-remainder) Pnr cent gielgdh '{ensilgl gielgdm 'ltrensglgl I c on as on 5 ram; s on s on La Mn tion 2 in lbs./sq. in lbs./sq. in lbs./sq in lbs./sq:

inches in. in. in.

The properties in the above table listed under the section headed by the term annealed were obtained by first rolling the alloys at a temperature between about 550-800 F. and thereafter annealing them at various temperatures in the temperature range from 400-800 F. The properties selected for the table were those of the annealed specimens which exhibited the maximum elongation. The properties listed under the section headed by the term cold rolled" were obtained by subjecting specimens of the alloys, which had been hot rolled at from 550-800 F. to additional rolling in the cold state. The properties selected forthe table were those of the cold rolled specimens which showed the greatest tensile and yield strengths, while having at least a 1 per cent elongation in 2 inches.

By a comparison of the properties listed in the above table, it will be observed that the combined properties of the new ternary alloy are superior to those of the related binary alloys having similar percentages of alloying ingredients, For example, it will be noted that the compositions containing the lower percentages of alloying ingredients show an exceptionally high elongation or ductility, while having superior yield and tensile properties in the annealed state; while those having higher percentages of alloying ingredients show high ductility coupled with exceptionally high yield and tensile strengths. Similarly, it will be noted that the properties of cold rolled specimens of the new alloy show improved strength characteristics.

These improvements are manifest throughout the range of alloying ingredients indicated.

While the new alloy is most useful in the wrought form, such as sheets, due to its formability characteristics, it may also be suitably used for making castings, forgings, extruded forms and the like.

The new alloy may be compounded by any of the methods usually employed for melting and alloying metals with magnesium, such as by adding the alloying ingredients singly or jointly to a bath of molten magnesium which is preferably protected from oxidation by a suitable flux.

1. A magnesium base alloy containing from 0.01 to 6 per cent of lanthanum and from 0.01 to 3 per cent of manganese, the balance being magneslum.

2. A magnesium base alloy containing from 0.1 to 1 per cent of lanthanum and from 1 to 3 per cent of manganese, the balance being magnesium.

3. A magnesium base alloy containing from 2 to 6 per cent of lanthanum and from 1 to 3 per cent of manganese, the balance being magnesium.

4. A magnesium base alloy containing from about 0.01 to 6 per cent of lanthanum and from 0.01 to 3 per cent of manganese, said alloy being characterized by having a higher degree of tensile strength, yield strength, and formability than a similar magnesium base alloy without the lanthanum.

JOHN C. MCDONALD. 

